Copper-based alloys and their use for infiltration of powder metal parts

ABSTRACT

Described are wrought forms of copper alloys for infiltrating powder metal parts, the method for preparing the copper alloys and their wrought forms, the method for their infiltration into a powder metal part, and the infiltrated metal part infiltrated with the novel alloys having a generally uniform distribution of copper throughout and exhibiting high transverse rupture strength, tensile strength and yield strength. Infiltrated metal parts prepared by infiltrating powder metal parts with reduced amounts of the novel infiltrant typically weigh less and have superior strengths compared to similarly prepared infiltrated metal parts prepared with standard methods and conventional infiltration.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of U.S. patentapplication Ser. No. 12/533,624, filed Jul. 31, 2009, which is acontinuation application of U.S. patent application Ser. No. 11/970,200,filed Jan. 7, 2008, which is a divisional application claiming priorityfrom U.S. patent application Ser. No. 11/348,975, filed Feb. 7, 2006,and now issued as U.S. Pat. No. 7,341,093, which claimed priority fromU.S. Provisional Patent Application Ser. No. 60/652,333, filed on Feb.11, 2005. Each of the above-referenced applications is herebyincorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to the manufacture and use of metalalloys, and in particular, to the use of metal alloys to infiltratepowder metal parts. Metal powder can be used to economically form avariety of complex-shaped metallic components or compacts by using apressing and sintering process. Use of this method provides a powdermetal part in near net shape, i.e., in the final desired size and shape,with minimal or no machining required. However, the resulting powdermetal parts are loosely held together and exhibit relatively low impactand fatigue strength. These properties can be improved by infiltratingthe parts with infiltrants that are typically copper based powders thatmay contain optional components such as, for example, lubricants andgraphite. The infiltrant powder infiltrates the porous structure of thepowder metal parts during the sintering process. The infiltrant powdersare typically a mixture of copper and one or more additional metals.

The infiltration process for a copper-based infiltrant generally beginsby placing the copper-based powder infiltrant in contact with thepressed and/or sintered powder metal part and subjecting thiscombination to a heating process which melts the copper-based powder. Asthe infiltrant powder melts, the molten material flows into thecompact's pores. Components of the infiltrant can melt and diffuse intothe compact at different rates. As a result, the distribution of copperthroughout the infiltrated powder metal part can vary. Infiltratedarticles having an uneven distribution of copper are more subject torupture when subjected to a variety of forces.

Typically, a supplier or user of the infiltrant will press theinfiltrant powder into a particular shape, such as a hollow cylinder,briquette, or pellet, to facilitate handling, shipping and/or storage,and to maximize its surface area that is in contact with the articlebeing infiltrated. In these various forms the pressed infiltrantcompacts can then be transported and utilized in a variety ofinfiltration processes. However, these pressed infiltrant compactsremain fragile and subject to breakage during their shipment andhandling. This breakage increases waste and handling costs as well asenvironmental costs incurred to manage the resulting infiltrantparticles or dust that can become suspended in the air and ultimatelysettle on work-surfaces. Workers must be protected from inhalation ofthis dust, so its removal from the workplace is necessary. Therefore, inlight of the above, improved infiltrants and methods for theirincorporation into powder metal parts are needed. Such improvedinfiltrants and methods for their use should avoid a majority of thedisadvantages of the infiltrating powders described above. Particularly,such improved infiltrants should not be subject to breakage andpowdering, should melt within a generally narrow temperature range, uponinfiltration into a powder metal compact, provide generally uniformcopper levels and impart strength to infiltrated article sufficient forits intended use. The present disclosure addresses these needs.

SUMMARY

One aspect of the disclosure provides a method for infiltrating a powdermetal part with a wrought form of a metal alloy. The process can includeselecting the powder metal part, selecting the metal alloy having awrought form adapted to contact a portion of the surface of the powdermetal part, contacting the surface of the metal part with the alloy andheating the alloy to a temperature sufficient to cause the alloy to meltand infiltrate the powder metal part.

A variety of powder metal parts are suitable for infiltration with thenovel alloy provided its components melt at a temperature higher thanthe alloy. In addition to the conventional iron-based powder metalparts, powder metal parts can also be based on a variety of othermaterials including, but not limited to stainless steel, nickel basedalloys, cobalt based alloys and systems comprising refractory metals.The term “powder metal part” is intended to broadly cover any powdermetal part that can be infiltrated with a copper-based alloy to form amore dense metal part.

In one embodiment, the metal alloy comprises copper, iron, and,optionally, manganese, and zinc, with copper being the major component.In a preferred embodiment, the copper-based alloy includes at leastabout 85 weight % copper, about 0.5 to about 3.5 weight % iron, about0.5 to about 5.5 weight % manganese, and about 0.5 to about 5.5 weight %zinc. The copper-based alloy can include minor amounts of variousimpurities or tramp elements without significantly affecting theprocessing parameters and/or the properties of the final infiltratedproduct.

The process of infiltration according to the present disclosure caninclude contacting the powder metal part with a wrought form of an alloyinfiltrant; subjecting the combined components to a heat treatment,including either a one-step or a two stage process; and subjecting thehot infiltrated part to a cool down cycle to solidify the infiltrant.During the heat treatment the alloy is heated to a sufficiently hightemperature to form a molten alloy that flows into the pores of thepowder metal part. This process provides an infiltrated powder metalpart that exhibits greater wear resistance and increased strength atlower infiltration levels compared to parts infiltrated by other knownprocesses and with other known infiltrants. The process can be conductedin a variety of atmospheric conditions such as, for example, a vacuum orpartial vacuum, or a highly-reducing atmosphere which can includenitrogen and/or hydrogen or an endothermic atmosphere.

In another aspect of the disclosure, an infiltrated metal part preparedaccording to the method of the disclosure exhibits a generally uniformdistribution of copper throughout and improved mechanical propertieswhich include, but are not limited to, increased transverse rupturestrength, increased tensile strength, and increased yield strength,compared to a metal part infiltrated using a known infiltration method.The improved strengths are particularly noted at lower infiltrationlevels.

One further aspect of this disclosure includes the method for preparingan infiltration alloy in a form having a three-dimensional form. Themethod comprises forming a mixture containing at least about 85 weight %copper, about 0.5 to about 3.5 weight % iron, about 0.5 to about 5.5weight % manganese, and about 0.5 to about 5.5 weight % zinc; heatingthe mixture to a temperature sufficient to form a homogeneous moltenmass; transferring the molten mass into a three-dimensional form andsolidifying said formed molten mass by cooling. Further objects,embodiments, forms, benefits, aspects, features and advantages of thedisclosure may be obtained from the description, drawings, and claimsprovided herein.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary powder metal part showingan alloy infiltrant in accordance with an aspect of the disclosure,illustratively shown in the shape of a flexible wire.

FIG. 2 is a perspective view of an exemplary powder metal part showingan alloy infiltrant in accordance with an aspect of the disclosure,illustratively shown in the form of a ring or washer.

FIG. 3 is a perspective view of an exemplary powder metal part showingan alloy infiltrant in accordance with an aspect of the disclosure,illustratively shown in the form of a disk.

FIG. 4 is a perspective view of an exemplary powder metal part showingan alloy infiltrant in accordance with an aspect of the disclosure,illustratively shown in the form of a wafer.

FIG. 5 shows the image of an XF-5 powder particle in cross section anddot maps for Mn, Fe and Zn derived from a SEM-EDS analysis.

FIG. 6 shows the image of the wire alloy in cross section and dot mapsfor Mn, Fe and Zn derived from a SEM-EDS analysis.

FIG. 7 provides an SEM-EDS elemental analysis of the XF-5 powder.

FIG. 8 provides an SEM-EDS elemental analysis of the wire alloy.

FIG. 9 provides an SEM photo of loose particles of the XF-5 powder at a250× magnification with particle No.'s 1, 2, and 3 designated forfurther analysis.

FIG. 10 provides an SEM-EDS elemental analysis of particle No. 1 fromFIG. 9.

FIG. 11 provides an SEM-EDS elemental analysis of particle No. 2 fromFIG. 9.

FIG. 12 provides an SEM-EDS elemental analysis of particle No. 3 fromFIG. 9.

DETAILED DESCRIPTION

The present disclosure relates to wrought forms of metal alloys, amethod for preparing the alloys, a method for infiltrating a powdermetal part with the metal alloy, and the infiltrated metal parts made bythe novel process. The novel metal alloys are copper-based and typicallycontain in addition to copper, iron, zinc, and manganese, with themajority of the alloy being copper. To infiltrate a powder metal part orcompact, the copper-based alloy is placed in contact with the part andthe combination of the part and the alloy is subjected to a heattreatment to induce the alloy to melt, causing substantially all themolten alloy to flow into the part's pores. Upon cooling, the alloywithin the infiltrated part solidifies providing a generally uniformdistribution of copper throughout the powder metal part.

In a particular embodiment, the copper-based alloy has a nominalcomposition of about 0.5% to about 3.5% iron, about 0.5% to about 5.5%manganese, and about 0.5% to about 5.5% zinc, with the remainder (exceptfor tramp elements) as copper. Preferred copper-based alloys typicallycontain at least 85% copper. Suitable alloys can tolerate a variety oftramp elements including, but not limited to, nickel, tin, silicon,phosphorous, lead, and aluminum, each tramp element typically in anamount of less than about 0.01% by weight, without experiencingdeleterious effects to either the infiltration process or the resultinginfiltrated part. By varying the relative amounts of the alloy'scomponents, the alloy can be prepared to have a melting point suitablefor use in an infiltration process, typically between about 950 to about1150° C., thereby making it suitable for use in a variety ofinfiltration processes.

An infiltrant having a form suitable for use in accordance with thedisclosure can be prepared by a variety of methods. In one embodiment,the alloy's components are combined, heated to a temperature sufficientto form a homogeneous molten mass which then is cast or molded to form abillet. Billets formed can be extruded or rolled to provide wroughtforms including rods, tubes, sheets, and the like. An extruded alloy canalso be divided into segments or further processed by standard drawingmethods to form flexible wires. The wrought forms of the novel alloyhave a uniform composition and can be provided in or conformed into avariety of forms and/or shapes advantageous for use in an infiltrationprocess. In one embodiment, the copper based infiltrant is provided inthe form of a drawn wire that can be wound onto spools for efficienthandling. Segments of the wire can be removed in an appropriate amountand conformed to a appropriate for use in a particular infiltrationprocess. FIG. 1 illustrates a segment of wire 20 adapted to conform tothe surface of powder metal part 1 prior to infiltration. In aninfiltration process involving the infiltration of large numbers ofparts having a known size and shape, the alloy may be provided in formsthat include disks, washers, wafers, sheets, rings and other shapesuitable for a particular application. FIGS. 2, 3 and 4 illustrate aring or washer 21, a disk 22 and a wafer 23, adapted to conform to thesurface of powder metal parts 2, 3, and 4, respectively. As illustrated,each of these wrought forms of a washer or a disk should be sized forthe part to be infiltrated when formed, whereas alloy material in wireor wafer form can be sized and conformed to the desired shape at anytime prior to the infiltration process.

Although powder metal parts suitable for infiltration can be preparedfrom a variety of metal powders, iron-base metal parts are more commonlyused. Such powder metal parts, referred to as green parts, are typicallyprepared by known pressing or molding techniques and may be sintered orunsintered. The alloy infiltrant is then typically placed in contactwith the powder metal part. The combined components are then subjectedto a heat treatment. Although contact with the powder metal part iscommonly with a solid infiltrant, contact can also occur with molteninfiltrant. For example, by maintaining the infiltrant above the powdermetal part during the heating process, infiltrant contact can be delayedand limited to contact with only molten infiltrant alloy formed duringthe heating process. A variety of means can be envisioned to maintainthe infiltrant alloy over the powder metal part, depending on theinfiltrant's size and shape. The heat treatment can be one or morestages with an optional cool down cycle. Preferably, the heat process isdone in a reducing atmosphere and/or under partial vacuum.

In one form, the process involves contacting the powder metal part withthe alloy infiltrant. The combined parts are then subjected to asingle-stage heat treatment which includes gradually heating thecombined part and alloy infiltrant in a furnace under a reducingatmosphere at a temperature of between about 950° C. (1750° F.) to about1150° C. (2100° F.) until the alloy is molten or liquid. The combinedparts are subjected to the heat treatment for a time period sufficientto allow infiltration of the molten alloy into the pores in the greenpowder metal part. In certain embodiments, this time period can rangebetween about 2 minutes to about 90 minutes. The amount of infiltrant,the temperature and/or the time of the process can be adjusted asdesired to provide parts having a range of infiltrant densities up to auniform density throughout the powder metal part.

For a two-stage heat treatment, the powder metal part is first treatedto a high temperature sintering process. The high temperature processsubjects the powder metal part to a temperature range between about 950°C. (1750° F.) to about 1150° C. (2100° F.) for a time period rangingbetween about 5 minutes to about 40 minutes. Thereafter, the powdermetal part and infiltrant alloy can then be recycled through the samefurnace under different conditions or sent directly to a second furnace.The second heat treatment can include sintering the combined parts. Thisprocess can be performed at a temperature between about 950° C. (1750°F.) to about 1150° C. (2100° F.) for a time period between about 5minutes and about 90 minutes. In particular embodiments, both the firstand second stage heat treatments are performed under a reducingatmosphere and/or under a partial vacuum. After the parts have undergonethis infiltration treatment, the infiltrated metal part can then beallowed to cool down in a cool-down cycle.

The infiltrant and infiltration processes according to the presentdisclosure offer particular advantages. For example, the copper-basedpowder infiltrants composed of a mixture of components are subject toparticle segregation that can result in composition differences fromsample to sample. Additionally, the different powder components can meltand infiltrate at different rates and/or temperatures. Unlike thecopper-based powder infiltrants, the wrought infiltrant is has a uniformcomposition that remains constant from sample to sample. Further, thewrought alloy melts and infiltrates uniformly. Additionally, thepreferred process can be performed without the necessity of aninfiltrant lubricant, such as, for example, metallic stearate orsynthetic wax, yet still permits essentially complete infiltrantdensification of the powder metal part, i.e., an infiltrated densityapproaching 100% when desired. It should be understood by those skilledin the art that the processes can be modified to fabricate aninfiltrated powder metal part or compact having a range of desiredinfiltrant density, such as for example, a density between 85% and 99%.

This infiltration process can provide infiltrated articles that changevery little in shape as a result of the infiltration process, yet areessentially 100% infiltrated, i.e., greater than 98% of infiltrateddensity. Alternatively, by varying the conditions (e.g., the temperatureranges, the time period for the heat treatment, and/or the amount ofcopper in the infiltrant), varying degrees of infiltrated density can beafforded to the powder metal part. Therefore, under a judiciousselection of process conditions and amount of the copper-based alloyinfiltrant, a final infiltrated metal part can be provided to have aninfiltrated density between about 85% and about 98%+ dense. Depending onthe powder metal part's porosity, the weight of the powder metal articlecan be increased by an amount between about 8 wt % and 20 wt % using acopper base alloy infiltrant in accordance with the disclosure. Becausethe zinc component of the alloy is more volatile than the othercomponents, an infiltrated powder metal part infiltrated with a copperalloy according to the present disclosure can, depending on theinfiltration conditions, contain reduced levels of zinc, withoutaffecting the metal part's performance.

The process according to the disclosure can provide an infiltratedmaterial with extremely high infiltration efficiency and productivity,eliminating secondary operations commonly associated with infiltrationprocesses. The high infiltration efficiency reduces the amount of lossof the infiltrant material, reduces processing costs, and minimizescleanup costs and EPA/OSHA concerns. Furthermore, applicant's methodutilizes infiltrants that require no compaction tooling and are easy tohandle, produces infiltrated articles that exhibit increased density,are generally free from erosion and residue from the infiltrant, andtypically exhibit superior properties. These superior propertiesgenerally include, for example: 1) generally uniform copperdistribution, 2) increased transverse rupture strength, 3) increasedtensile strength, 4) increased yield strength, and 5) increased strengthindices.

The strength indices are derived from the ratio of a particular strengthdivided by the density of the infiltrated article. For example, theformula for the transverse rupture strength (TRS) index is:

$\begin{matrix}{{T\; R\; S\mspace{14mu} {index}} = \frac{T\; R\; S\mspace{14mu} ({psi})}{{density}\mspace{14mu} \left( {g\text{/}{cm}^{3}} \right) \times 10^{4}\mspace{14mu} \left( {{scaling}\mspace{14mu} {factor}} \right)}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

The Tensile Strength (TS) Index and the Yield Strength (YS) Index can becalculated from this formula by substituting the Tensile Strength andthe Yield Strength for the Transverse Rupture Strength. A strength indexprovides information about the level of strength achieved with a unitmass of metal and is independent of a standard article. Maximizing thestrength of an article without increasing its weight is an importantobjective in designing equipment that is lightweight and easy to handle,as in the case of fuel efficient motor vehicles. A modified strengthindex (SI*) can additionally reflect both the density of the infiltratedarticle and the % infiltration. The Modified strength Index can becalculated from the formula:

$\begin{matrix}{{{Modified}\mspace{14mu} T\; R\; S\mspace{14mu} {Index}\mspace{14mu} \left( {S\; I^{*}} \right)} = \frac{T\; R\; S\mspace{14mu} ({psi})}{{density}\mspace{14mu} \left( {g\text{/}{cm}^{3}} \right) \times \left( {\% \mspace{14mu} {infiltration}}\; \right)^{4}}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

The Modified Tensile Strength Index (TS SI*) and the Yield StrengthIndex (YS SI*) can be calculated from this formula by substituting theTensile Strength and the Yield Strength for the Transverse RuptureStrength.

The present disclosure contemplates modifications as would occur tothose skilled in the art. It is also contemplated that individual stepsin the processes embodied in the present disclosure can be altered,deleted, duplicated, or added to other processes as would occur to thoseskilled in the art without departing from the spirit of the presentdisclosure. In addition, the various stages, techniques, and operationswithin these processes may be altered as would occur to those skilled inthe art. Further, any theory of operation, proof, or finding statedherein is meant to further enhance understanding of the presentdisclosure and is not intended to make the scope of the presentdisclosure dependent upon such theory, proof, or finding.

The following examples illustrate some of the improved propertiesrealized in accordance with particular embodiments of the disclosure.

Example 1 Preparation of Raw Compacts for Infiltration

Un-sintered compacts for test specimens were prepared by compacting apowder mixture of Atomet 28 iron powder, 0.9 weight % graphite and 0.75weight % Acrawax C lubricant. Atomet powder is available from QuebecMetal Powder Ltd., 1655 Route Marie-Victorin Tracy, Quebec Canada J3R4R4 and Acrawax C lubricant is available from Lonza Inc., 3500 TrentonAve. Williamsport, Pa. 17701. Acrawax is a registered trademark of Chas.L. Huisking & Co., Inc., 417 5^(th) Ave. New York, N.Y. Porous compacts,6-1 through 6-5 and 7-1 through 7-5 having a rectangular shape,nominally 1.25 inches long, 0.50 inches wide and 0.25 inches thick anddensities of about 6.7 and 7.0 g/cm³ were prepared for infiltration. Asillustrated in Table I, the green compacts were measured prior toinfiltration.

TABLE I Raw Compacts - Atomet 28 Powder Sample Density Width OverallLength Weight ID g/cm³ Inch(s) Inch(s) g 6-1 6.67 0.5014 0.2435 16.6716-2 6.65 0.5013 0.2367 16.158 6-3 6.68 0.5013 0.2351 16.126 6-4 6.680.5012 0.2381 16.348 6-5 6.67 0.5014 0.2427 16.625 7-1 6.93 0.50250.2509 17.896 7-2 6.96 0.5020 0.2510 17.955 7-3 6.95 0.5017 0.255618.260 7-4 6.97 0.5022 0.2524 18.090 7-5 6.96 0.5023 0.2477 17.737

Example 2 Infiltration of Compacts

Individual sections of a wire alloy containing about 93% copper, about3% manganese, about 3% zinc and about 1% iron were selected and readiedfor infiltration. Lengths of the wire alloy weighing about 2.4 g wasplaced on the top of each of samples 6-1 through 6-5 and samples 7-1through 7-5 and the samples sintered at about 1125° C. for about 30minutes under a 90/10 nitrogen/hydrogen atmosphere, then allowed to coolto ambient temperature. The resulting infiltrated compacts werere-measured as illustrated in Table II. Similar results can be obtainedwith segments of wire alloy having as little as about 85% copper.

TABLE II Infiltration Data - A Overall Sample Infiltrate Density WidthLength Weight ID gm/% g/cm³ Inch(s) Inch(s) g 6-1 2.33/13.9 7.51 0.50080.2440 18.789 6-2 2.33/14.4 7.58 0.5006 0.2348 18.264 6-3 2.33/14.4 7.610.5007 0.2345 18.320 6-4 2.33/14.3 7.63 0.5014 0.2378 18.659 6-52.53/15.2 7.56 0.5015 0.2426 18.863 7-1 2.38/13.3 7.81 0.5019 0.249220.061 7-2 2.44/13.6 7.80 0.5021 0.2509 20.174 7-3 2.44/13.4 7.83 0.50250.2553 20.616 7-4 2.44/13.5 7.78 0.5022 0.2530 20.293 7-5 2.47/13.9 7.830.5020 0.2477 19.987

Example 3 Determination of Transverse Rupture Strength and Hardness

The transverse rupture strength and hardness (HRB and HRC) of certain ofthe infiltrated compact samples were determined by the followingmethods: MPIF Standard Test Method #41 and MPIF Standard Test Method#43. The results obtained are provided in Table III.

TABLE III Mechanical Strength - A Transverse Hard- Hard- Sample % Infil-Density Rupture Strength ness ness ID tration g/cm³ Psi SI SI* HRB HRC6-2 14.4 7.58 225,400 2.98 0.71 — 23-17 6-4 14.3 7.63 197,100 2.58 0.65102 25-19 6-5 15.2 7.56 224,500 2.97 0.57 101 24-16 Average 14.6 7.59215,000 2.83 0.64   101.5 24-17 7-1 13.3 7.81 239,200 3.06 1.01 — 28-237-3 13.4 7.83 196,700 2.51 0.80 — 30-25 7-4 13.5 7.78 221,000 2.84 0.78106 30-24 Average 13.4 7.81 219,000 2.80 0.87 106 29-24

Example 4 Determination of Tensile Strength, Yield Strength and %Elongation

Samples 6-6 through 6-10 and 7-6 through 7-10 were prepared as describedabove and sintered with 12.1% and 11.4% of the wire infiltrant,respectively. The samples were formed in the shape of flat tensilespecimens. The tensile strength, yield strength and % elongation of eachsample was determined by MPIF Standard Method #10. The results forsamples 6-6 through 6-10 and 7-6 through 7-10 are provided in Table IV.

TABLE IV Mechanical Strength - B Green Infiltrated Sample DensityDensity Tensile Strength Yield Strength ID g/cm³ g/cm³ psi SI SI* psi SISI* % Elongation 6-6 6.7 7.45 115,000 1.54 0.72 85,000 1.14 0.53 2.7 6-76.7 7.44 116,000 1.56 0.73 90,000 1.21 0.57 — 6-8 6.7 7.43 107,000 1.440.67 84,500 1.14 0.53 2.8 6-9 6.7 7.45 114,000 1.53 0.72 86,500 1.160.54 2.7 6-10 6.7 7.44 116,000 1.56 0.73 86,500 1.16 0.54 2.7 Average6.7 7.44 114,000 1.53 0.72 86,500 1.16 0.54 2.7 7-6 7.0 7.68 121,0001.58 0.93 90,500 1.18 0.70 2.5 7-7 7.0 7.67 132,000 1.72 1.02 95,0001.24 0.73 3.3 7-8 7.0 7.67 127,000 1.66 0.98 94,000 1.23 0.73 — 7-9 7.07.63 129,000 1.70 1.00 94,000 1.23 0.73 3.1 7-10 7.0 7.66 126,000 1.640.97 98,000 1.28 0.76 3.0 Average 7.0 7.66 127,000 1.66 0.98 94,300 1.230.73 3.0

Example 5 Determination of Impact Energy

Samples 6-11 through 6-15 and 7-11 through 7-15 were prepared asdescribed above and sintered with 13.4% and 12.9% of the wireinfiltrant, respectively. The samples were formed in the shape of Izodimpact energy test specimens (i.e., 75 mm in length, 10 mm in width andthickness). The Impact Energy of the infiltrated samples was determinedby MPIF Standard Test Method #40. The results for samples 6-11 through6-15, 7-11 through 7-15 are provided in Table V.

TABLE V Infiltration Data - B Sample Green Infiltrated Impact ID Densityg/cm³ Density g/cm³ Energy ft-lbf 6-11 6.7 7.60 10 6-12 6.7 7.56 13 6-136.7 7.59 12 6-14 6.7 7.59 12 6-15 6.7 7.57 10 Average 6.7 7.58 11.4 7-117.0 7.81 14 7-12 7.0 7.82 8.5 7-13 7.0 7.78 9 7-14 7.0 7.78 10 7-15 7.07.80 17 Average 7.0 7.80 11.7

Example 6 Comparison of the Properties of Infiltrated Articles UsingDifferent Infiltrants

Summarized below in Table VI is a comparison of the mechanical strengthof compacts infiltrated with the alloy (in wire form) of the presentdisclosure and a copper alloy in powder form. Summarized in Tables VIIand VIII are tabulations illustrating the % increases in transverserupture strength, tensile strength and yield strength achieved by theimproved infiltration processes described above.

TABLE VI Mechanical Strength - Summary and Comparison Transverse TensileYield Rupture Impact Density Strength Strength % Strength HardnessEnergy Material g/cm³ psi psi Elongation psi HRB/HRC ft-lbf MPIF 7.387,000 60,000 3 166,000 89 10 FX-1008* Alloy in 7.44-7.59 114,000 86,5002.7 215,000 101/21 11.4 wire form** Alloy in 7.66-7.81 127,000 94,300 3219,000 106/27 11.7 wire form** *The properties for MPIF FX-1008 werereproduced from “Materials Standards for P/M Structural Parts”, page 23,(2003) published by Metal Powder Industries Federation, 105 College RoadEast, Princeton, New Jersey 08540-6692. **The single values are averagevalues from Tables III, IV, and V

Summarized below in Table VII are comparisons of the % increases in thetransverse rupture strength, the tensile strength and the yield strengthof powder metal compacts infiltrated with an alloy of the presentdisclosure (in wire form) and the known powder metal infiltrated steelMPIF FX-1008 (infiltrant in powder form) as well as the various strengthindices (S.I.'s) for the samples.

TABLE VII Strength Comparisons Transverse Rupture Sample StrengthTensile Strength, Yield Strength ID % Increase S.I. % Increase S.I. %Increase S.I. MPIF 0  2.3 0  1.2 0  0.8 FX- 1008 6-2 35.8 3.0 — — — —6-4 18.8 2.9 — — — — 6-5 35.2 3.0 — — — — 7-1 44.1 3.1 — — — — 7-3 18.52.5 — — — — 7-4 33.1 2.8 — — — — Average 30.9 2.9 — — — — 6-6 — — 17.21.5 41.7 1.1 6-7 — — 33.3 1.6 50.0 1.2 6-8 — — 22.9 1.4 40.8 1.1 6-9 — —31.0 1.5 44.2 1.2 6-10 — — 33.3 1.6 44.2 1.2 Average — — 21.3 1.5 36.21.2 7-6 — — 39.1 1.6 50.8 1.2 7-7 — — 51.7 1.7 58.3 1.2 7-8 — — 45.9 1.756.7 1.2 7-9 — — 48.3 1.7 56.7 1.2 7-10 — — 44.8 1.6 63.3 1.3 Average —— 46.0 1.7 57.2 1.2

Example 7 The Distribution of Copper in the Infiltrated Metal Part

Infiltrated samples designated 6-4 and 7-4 as described in Example 2above, were analyzed for copper content at a depth of 0.025 of an inchfrom the top and bottom surfaces. The top and bottom copper levels forsample 6-4 were 13.2 weight % and 12.8 weight %, respectively. The topand bottom copper levels for sample 7-4 were 11.0 weight % and 11.0weight %, respectively. Thus a generally uniform distribution of copperthroughout the infiltrated powder metal part was attained.

Example 8 Infiltration to Intermediate and Maximum Levels

The procedures of Examples 1 through 5 were repeated with a wire alloycomprising 91.6% copper, 1.9% iron, 2.6%, manganese and 3.9% zinc,except that higher levels of infiltrant were used to determine the upperlevel of infiltration possible with the novel wire alloy. Infiltrationof 14.1% of the alloy proceeded normally, whereas infiltration with asmuch as 14.3% resulted in some small quantity of copper pooling on thesurface of some of the specimens. The properties of the resultinginfiltrated compacts corresponding to the material designation MPIFFX-1008 are provided in Tables VIII, IX, and X, below.

TABLE VIII Green—In- filtrated Transverse Rupture Hardness Sample %Infil- Density Strength Top/Bottom I.D. trate g/cm³ Psi SI* HRC/HRB 6-1610.9 6.76—7.40 192,100 1.84 97/93 6-17 10.9 6.75—7.39 185,700 1.78 90/916-18 10.9 6.75—7.39 182,800 1.81 91/91 6-19 10.9 6.74—7.39 189,500 1.8292/92 6-20 10.9 6.75—7.38 182,600 1.75 92/90 Average 10.9 6.75—7.39187,000 1.81 92/91 6-21 14.1  6.7—7.63 201,400 0.65 26/96 6-22 14.1 6.7—7.61 184,000 0.60 28/97 6-23 14.1  6.7—7.61 194,100 0.63 29/96 6-2414.1  6.7—7.60 199,200 0.65 28/95 6-25 14.1  6.7—7.61 193,900 0.63 28/95Average 14.1  6.7—7.61 194,600 0.63 28/96 7-16 10.8 6.95—7.59 202,6001.96 29/96 7-17 10.8 6.95—7.62 199,700 1.93 28/95 7-18 10.8 6.95—7.65211,800 2.04 28/95 7-19 10.8 6.95—7.65 214,800 2.06 28/95 7-20 10.86.95—7.66 204,200 1.96 27/97 Average 10.8 6.95—7.63 206,600 1.99 28/967-21 13.6 6.95—7.73 227,200 0.86 32/24 7-22 13.6 6.95—7.69 206,600 0.793225 7-23 13.6 6.95—7.81 210,300 0.79 32/24 7-24 13.6 6.95—7.82 213,1000.80 32/24 7-25 13.6 6.95—7.72 223,600 0.85 32/24 Average 13.6 6.95—7.75216,200 0.82 32/24

TABLE IX Green-Infiltrated Tensile Sample % Density Strength YieldStrength % ID Infiltrant g/cm³ Psi SI* psi SI* Elongation 6-26 10.96.66-7.30 105,000 1.02 83,600 0.81 2.0 6-27 10.9 6.66-7.28 99,500 0.9782,800 0.81 1.5 6-28 10.9 6.62-7.27 105,000 1.02 84,100 0.82 2.5 6-2910.9 6.64-7.27 104,000 1.01 86,400 0.84 1.0 6-30 10.9 6.65-7.29 107,0001.04 93,700 0.91 5.0 Average 10.9 6.65-7.28 104,000 1.01 86,100 0.84 2.46-31 13.9  6.7-7.58 121,000 0.43 89,500 0.32 1.0 6-32 13.9  6.7-7.61124,000 0.44 92,500 0.33 1.0 6-33 13.9  6.7-7.62 120,000 0.42 91,0000.32 1.5 6-34 13.9  6.7-7.56 118,000 0.42 90,500 0.32 1.5 6-35 13.9 6.7-7.53 120,000 0.43 91,000 0.33 1.3 Average 13.9 6.77-7.58 120,0000.42 91,000 0.32 1.3 7-26 10.9 6.95-7.72 120,000 1.10 95,000 0.87 1.07-27 10.9 6.95-7.72 124,000 1.14 100,000 0.92 1.5 7-28 10.9 6.95-7.71126,000 1.16 96,000 0.88 1.5 7-29 10.9 6.95-7.74 124,000 1.14 96,0000.89 1.5 7-30 10.9 6.95-7.70 122,000 1.12 93,500 0.86 1.0 Average 10.96.95-7.72 123,000 1.13 96,000 0.88 1.3 7-31 14.3 6.95-7.90 122,000 0.3793,500 0.28 1.5 7-32 14.3 6.95-7.85 124,000 0.38 97,500 0.28 1.5 7-3314.3 6.95-7.90 126,000 0.38 110,000 0.33 1.0 7-34 14.3 6.95-7.87 121,0000.37 95,000 0.29 1.0 7-35 14.3 6.95-7.81 120,000 0.37 94,000 0.29 1.0Average 14.3 6.95-7.87 123,000 0.37 98,000 0.30 1.2

TABLE X Sample % Green—Infiltrated Impact I.D. Infiltrant Density g/cm³Energy Ft-lbf 6-36 10.9 6.75—7.40 15 6-37 10.9 6.76—7.42 15 6-38 10.96.73—7.39 14 6-39 10.9 6.74—7.41 14 6-40 10.9 6.77—7.42 14.5 Average10.9 6.75—7.41 14.5 6-41 14.1  6.7—7.57 9.0 6-42 14.1  6.7—7.57 12.06-43 14.1  6.7—7.60 11.5 6-44 14.1  6.7—7.60 10.5 6-45 14.1  6.7—7.5811.5 Average 14.1  6.7—7.59 11.0 7-36 10.7 6.95—7.60 12.5 7-37 10.76.95—7.61 12.5 7-38 10.7 6.95—7.60 15.0 7-39 10.7 6.95—7.59 13.5 7-4010.7 6.95—7.61 10.5 Average 10.7 6.95—7.60 13.0 7-41 13.8 6.95—7.79 14.57-42 13.8 6.95—7.78 10.0 7-43 13.8 6.95—7.78 8.5 7-44 13.8 6.95—7.7414.0 7-45 13.8 6.95—7.67 10.0 Average 13.8 6.95—7.77 11.0

Example 9 Infiltration with a Powder Alloy Compact

The procedures of Example 8 were repeated with a powdered alloy XF-5,(available from U.S. Bronze, 18649 Brake Shoe Road, Meadville, Pa.) thatcomprised 94.1% copper, 1.7% iron, 2.8% manganese, and 1.4% zinc to forminfiltrated compacts corresponding to the material designation MPIFFX-1008. The results obtained are provided in Tables XII, XIII, and XIV,provided below.

TABLE XII Green- % Sam- Infiltrated Tensile Elon- ple % Density StrengthYield Strength ga- I.D. Infiltrant g/cm³ Psi SI* psi SI* tion 6-31 13.56.7-7.36 120,000 0.49 90,000 0.37 1.0 6-32 13.5 6.7-7.40 118,000 0.4890,000 0.37 1.0 6-33 13.5 6.7-7.44 118,000 0.48 90,000 0.36 1.0 6-3413.5 6.7-7.34 119,000 0.49 94,000 0.39 1.0 6-35 13.5 6.7-7.34 111,0000.46 88,500 0.36 1.0 Aver- 13.5 6.7-7.38 117,000 0.48 90,500 0.37 1.0age

TABLE XIII Sample % Green—Infiltrated Impact I.D. Infiltrant Densityg/cm³ Energy ft-lbf 6-36 13.5 6.7—7.47 10.5 6-37 13.5 6.7—7.48 11.5 6-3813.5 6.7—7.50 11.0 6-39 13.5 6.7—7.48 14.0 6-40 13.5 6.7—7.51 14.5Average 13.5 6.7—7.49 12.3

TABLE XIV Green—In- filtrated Transverse Rupture Hardness Sample %Infil- Density Strength Top/Bottom I.D. trant g/cm³ psi SI* HRC/HRB 6-4113.5 6.7—7.49 193,300 0.78 25/95 6-42 13.5 6.7—7.48 195,600 0.79 23/956-43 13.5 6.7—7.56 186,800 0.74 25/95 6-44 13.5 6.7—7.54 182,000 0.7325/95 6-45 13.5 6.7—7.55 186,200 0.75 25/95 Average 13.5 6.7—7.52188,800 0.76 25/95

Table XV, provided below, summarizes the data averages from tables IIIthrough XIV. Articles infiltrated with in the order of 10-11% of thewire infiltrate have transverse rupture strengths, tensile strengths andyield strengths substantially greater than articles infiltrated with asmuch as 13.5% of a powder infiltrant. Even as the strength measurementscoalesce at full or nearly complete infiltration, the wire infiltranttypically provides a greater measure of strength than the powderinfiltrant.

TABLE XV % Green/infiltrated Run Infiltrant density TRS TRS-SI* TSTS-SI* YS YS-SI* 6-2/6-5 14.6 6.67/7.59 215,000 0.64 6-21/6-25 14.1 6.7/7.61 194,600 0.63 6-16/6-20 10.9 6.75/7.39 187,000 1.81 6-41/6-4513.5*  6.7/7.52 188,800 0.76 7-21/7-25 13.6 6.95/7.75 216,200 0.827-1/7-4 13.4 6.96/7.81 219,000 0.87 7-16/7-20 10.8 6.95/7.63 206,6001.99 7-16/7-20 10.8 6.95/7.63 206,600 1.99 6-31/6-35 13.9 6.77/7.58120,000 0.42 91,000 0.32  6-6/6-10 12.1  6.7/7.44 114,000 0.72 86,5000.54 6-26/6-30 10.9 6.65/7.28 104,000 1.10 86,100 0.84 6-31/6-35 13.5* 6.7/7.38 117,000 0.48 90,500 0.37 7-31/7-35 14.3 6.95/7.87 123,000 0.3798,000 0.30  7-6/7-10 11.4  7.0/7.66 127,000 0.98 94,300 0.73 7-26/7-3010.9 6.95/7.72 123,000 1.13 96,000 0.88 *Powder infiltrant was usedrather than the wire alloy infiltrant

Table XVI, provided below summarizes selected data from tables VIIIthrough XIV. This summarized data illustrates the ability of lowerlevels of the wire alloy infiltrant to: a) provide equal or superiormechanical properties, b) more efficiently infiltrate to achieve higherdensity infiltrated compacts, and (c) reduce the infiltrated compact'scost by reducing the amount of infiltrate required. The ability toachieve superior mechanical properties by infiltrating a higher densitygreen compact with a lesser quantity of wrought alloy infiltrant (24-26%less) can provide significant cost savings.

TABLE XVI XF-5 Wire Wire Powder Alloy Alloy Alloy Green Density, g/cm³from 6.65 6.95 6.7 to 6.75 Infiltrated Density, g/cm³ 7.28-7.417.60-7.72 7.38-7.52 % Infiltration 10.9  10.7-10.9% 13.5% RelativeAmount of 1 1 1.24-1.26 Infiltrant Tensile Strength, psi 104,000* 123,000 117,000 Yield Strength, psi 86,100*  96,000  90,500 TransverseRupture 187,000** 206,600 188,800 Strength, psi Impact Energy, Ft-lbf14.5** 13.5 12.3 % Elongation 2.4* 1.3 1.0 Hardness Top/Bottom,  92/91**28/96 28/95 HRC/HRB *data for 6.65 g/cm³ green density **data for 6.75g/cm³ green density

Example 10 Preparation of Novel Copper Infiltration Alloy

A mixture containing 92 parts by weight copper, 3 parts by weightmanganese, 3 parts by weight zinc and 2 parts by weight iron was heatedto about 2100° C. to form a homogeneous melt. The molten mass wastransferred into a mold, heat was removed and the billet formed wasremoved from the mold. The billet was superheated and extruded to formrods having a cross sectional diameter of about one fourth of an inch.In a similar manner the billet can be extruded to form tubes or rolledto form sheets. The rods formed were drawn into a wire having a diameterof about 0.093 inches. Similarly, the rods formed can be rolled to formsheets of the alloy. Infiltrants having disk and washer shapes can beformed from rods and tubes having a range of diameters by cutting therods and tubes across their longitudinal axis. Infiltrants having awafer shape can be formed from the alloy in sheet form or by cuttingsections of rods having a square, rectangular or other cross-sectionalshape. Infiltrants having a ring or torus shape can be formed from wireforms of the alloy. Wire forms of the alloy can be wound onto spools andthe like to simplify transportation, storage and handling. Because thewires have a generally uniform density, the weight of infiltrant can beconveniently related to the length of a section of wire or ribbon.

Copper alloys having as little as about 85 weight % copper, about 0.5 toabout 5.5 weight % manganese, about 0.5 to about 5.5 weight % zinc andabout 0.5 to about 3.5 weight % iron can be prepared according to thismethod and formed into the various forms of wrought infiltrant articlesdiscussed above. Such articles are particularly suitable for providinginfiltrated powder metal parts having superior physical properties.

Example 11 Chemical Analysis of XF-5 Powder Infiltrant and the WireAlloy Infiltrant

Samples of the XF-5 powder infiltrant available from U.S. Bronze and thewire alloy infiltrant (described in Example 8) of the present disclosurewere subjected to bulk analysis. Trace elements and minor impuritieswere not determined. The results are provided in Table XVII.

TABLE XVII Bulk Analysis of Powder and Wire Alloy Infiltrates XF-5 WireElement Powder Alloy Mn 2.8 2.6 Fe 1.7 1.9 Zn 1.4 3.9

Example 12 Distribution of Metals in XF-5 Powder and Wire Alloy

A portion of the XF-5 Powder was dispersed in an epoxy and cast into asample mold to form a composite sample. The composite's cross sectionwas polished to expose the cross-section of individual powder particles.The wire alloy was cross-sectioned and mounted to examine itslongitudinal direction (the wire drawn direction). Cross sections of thepowder composite and wire were examined by SEM-EDS analysis.

FIG. 5 shows the powder particle composite in cross-section and dot mapsof the elements Mn, Fe, and Zn. The number and distribution of dotsrepresents the amount of a metal element present and its distributionthrough the particle. FIG. 6 shows the wire alloy cross-section and dotmaps. A greater number of dots present represents a higher metal contentand the even distribution of dots represents an even distribution of themetal elements throughout the wire alloy. FIGS. 5 and 6 indicate thatthe powder contains lesser amounts of the metals evenly distributedthroughout the powder whereas the wire contains a large metal contentevenly distributed throughout the wire's cross-section.

Example 13 Evidence of Un-Alloyed Fe in the Non-Homogeneous XF-5 Powder

A small magnet was placed in a sample of the XF-5 powder infiltrant.Upon removing the magnet the tip was observed to be coated with finegrey particles aligned with the magnetic field of the magnet's tipindicating the presence of unalloyed iron particles in the XF-5 powder.

Example 14 The Elemental Analysis Spectrum of the XF-5 Powder and theWire Alloy

The elemental analysis spectrum of a sample of the bulk XF-5 powder wasmeasured and the results provided in FIG. 7. The presence of traceamounts of aluminum and titanium was noted. As expected, the copper isshown to be the major component. However, the iron levels appear to beslightly higher than the manganese levels, which is inconsistent withthe bulk analysis provided in Example 11. Although inconsistent with thebulk analysis, the result is consistent with the powder infiltrant beinga mixture of individual powder particles that can segregate and,depending on sampling and particle distribution, demonstrate variablecomposition from sample to sample.

The elemental analysis spectrum of the wire alloy was similarly measuredand the results provided in FIG. 8. The large unmarked peak to the leftof FIG. 8 is gold, which was sputter-coated onto the wire alloy sampleto ensure adequate conductivity. Like the powder, copper peaks are thelargest, copper making up more than 90% of the alloy. Unlike the powder,the manganese peak is higher than the iron peak, consistent with thebulk analysis. The elemental analysis of the wire alloy is consistentwith the wire alloy having a generally uniform composition.

Example 15 Elemental Analysis of Individual XF-5 Powder Particles

FIG. 9 shows a distribution of the XF-5 powder particles at 250×magnification. Individually selected particles designated by numerals 1,2, and 3 are noted. The individual elemental spectra for particles 1, 2,and 3 were measured and are provided in FIGS. 10, 11, and 12,respectively. As is evident from FIG. 10, particle 1 is a substantiallypure particle of manganese. The small copper peaks are backgroundreadings from larger nearby copper particles. As can be noted from FIG.11, particle 2 appears to be a brass particle having an approximately10% zinc content and minor amounts of titanium and iron impurities. Thespectrum of particle 3, shown in FIG. 12 indicates that particle 3 is anearly pure particle of copper. Based on the magnetic study (Example13), the elemental analysis (Example 14) and the analysis of individualXF-5 particles (this Example), the XF-5 powder is a non-homogeneousmixture of copper, a copper/zinc brass alloy, iron, and manganese. Incontrast, all of the spectral evidence provided indicates that the wirealloy is a substantially homogeneous alloy comprising copper, iron, zincand manganese.

While the disclosure has been illustrated and described in detail in theforegoing description and examples, the same is considered to beillustrative and not restrictive in character, it is understood thatonly the preferred embodiments have been shown and described and thatall changes and modifications that come within the spirit of thedisclosure are desired to be protected.

1. A method for infiltrating a powder metal part, the method comprising:a) providing the powder metal part; b) providing a copper alloy having ahomogeneous wrought form adapted to contact a surface of the powdermetal part, c) contacting the alloy with a surface of the powder metalpart; and d) heating the alloy and the powder metal part to atemperature sufficient to cause the alloy to melt and infiltrate thepowder metal part, wherein the alloy comprises: (i) at least about 85weight % copper; and ii) about 0.5 to about 3.5 weight % iron.
 2. Themethod of claim 1, wherein the alloy contains at least about 90 weight %copper.
 3. The method of claim 1, wherein the powder metal part is aniron-based powder metal part.
 4. The method of claim 3, wherein thepowder metal part is a sintered metal part.
 5. The method of claim 1,wherein the surface of the powder metal part is an upper surface.
 6. Themethod of claim 1, wherein the temperature is at least about 800° C. 7.The method of claim 1, wherein the homogeneous wrought form is a wiresegment.
 8. The method of claim 7, wherein the wire segment has agenerally torus shaped form.
 9. The method of claim 1, wherein thehomogeneous wrought form is a disk.
 10. The method of claim 1, whereinthe homogeneous wrought form is a washer.
 11. The method of claim 1,wherein the heating is conducted at less than atmospheric pressure. 12.The method of claim 1, wherein the heating is conducted in ahighly-reducing atmosphere.
 13. The method of claim 1, wherein thehomogeneous wrought form is a wafer.
 14. A method for infiltrating apowder metal part, the method comprising: a) providing the powder metalpart; b) providing a copper alloy having a homogeneous wrought form; (c)shaping the copper alloy to conform the alloy to a surface of the powdermetal part; d) contacting the shaped copper alloy with the surface ofthe powder metal part; and e) heating the alloy and the powder metalpart to a temperature sufficient to cause the alloy to melt andinfiltrate the powder metal part, wherein the alloy comprises: (i) atleast about 85 weight % copper; and ii) about 0.5 to about 3.5 weight %iron.
 15. The method of claim 14, wherein shaping the copper alloy toconform to the surface of a powder metal part involves a shaping processselected from the group consisting of forming a wire coil, forming adisk, forming a washer, forming a wafer, forming a sheet, and forming aring.
 16. The method of claim 15, wherein the shaping process selectedinvolves forming a wire coil.
 17. A method for infiltrating a powdermetal part, the method comprising: a) providing a copper alloy incontact with a surface of the powder metal part, and (b) heating thealloy and the powder metal part to a temperature sufficient to cause thealloy to melt and infiltrate the powder metal part; wherein the alloyhas a homogeneous wrought form and a shape adapted to contact a surfaceof the powder metal part, and wherein the alloy comprises: (i) at leastabout 85 weight % copper; and ii) about 0.5 to about 3.5 weight % iron.18. The method of claim 17, wherein providing a copper alloy in contactwith a surface of the powder metal part, involves providing a copperalloy having a shape selected from the group consisting of a wire coil,a disk, a washer, a wafer, a sheet, and a ring.